By all means remove all casting flash from all ports and get them as flawless as possible. But under no circumstances polish the inlet ports. Exhaust ports go for your life, just keep their shape. But if anyone tells you to polish the inlets NEVER see or talk to them again. They have no idea of what they're talking about. The burred surface causes the inlet mixture's boundary layer to swirl, not a lot just enough to keep the fuel suspended rather than fall out. And you want that fuel in the combustion chamber, don't you? Not excessively wetting the walls of the ports.